Process for Forming Polymer Blends

ABSTRACT

A method for forming a fiber, the method comprising charging to a reactive extruder a first polymer and a second polymer to form an initial blend, where the first polymer is a propylene-based elastomer including up to 35% by weight ethylene-derived units and a heat of fusion, as determined according to DSC procedures according to ASTM E-793, of less than 80 J/g and a melt temperature of less than 110° C., where the second polymer is a propylene-based polymer having a melt temperature in excess of 110° C. and a heat of fusion in excess of 80 J/g, and introducing the reactive blend to a spinneret to form a fiber or extruding the reacted blend through a plurality of die capillaries to form molten threads or filaments which are attenuated in a gas stream to form meltblown fibers.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part to U.S. application Ser. No.13/132,675, filed Aug. 29, 2011, which is a 371 National StageApplication of International Application No. PCT/US2009/067533, filedDec. 10, 2009, which claims priority to U.S. Provisional PatentApplication No. 61/141,164, filed Dec. 29, 2008, the disclosures ofwhich are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

Embodiments of the present invention are directed toward methods forforming blends of propylene-based elastomer and propylene-basedthermoplastic resin.

BACKGROUND OF THE INVENTION

Propylene-based elastomers, which may have been referred to assemi-amorphous propylene copolymers or crystallizable propylene-basedcopolymers, have been employed in the manufacture of fibers andnon-woven fabrics. These copolymers are often blended with otherpolymers in the pursuit of sundry desirable properties.

For example, U.S. Publication No. 2005/0107529 teaches fibers preparedfrom propylene-based elastomers. Examples 1-4 teach the production offibers from a melt that contains a 20 MFR propylene-ethylene copolymercontaining 15 weight percent ethylene together with a propylenehomopolymer. The propylene homopolymer is either a 36 MFR homopolymer ora 400 MFR homopolymer. The fibers are formed by employing a conventionalfiber spinning line under partially oriented yarn mode. The fibers andnon-wovens prepared therefrom can be heat set to provide durablefabrics.

U.S. Pat. No. 6,218,010 teaches an ethylene-propylene copolymer alloythat is suited for making fibers and non-woven spunbond fabrics havingsoftness at economically acceptable processing conditions. The alloycomprises a random copolymer having an ethylene content of from about 1to about 5% by weight in an amount of from about 40 to about 90% byweight of the alloy; and a second ethylene-propylene copolymer having anethylene content of from about 5 to about 40% by weight, in an amount offrom about 10 to about 60% by weight of the alloy. The copolymer alloysare described as prepared by a multi-reactor process comprising a firststage of polymerizing a mixture of ethylene and propylene in single orplural reactors, in the presence of a catalyst system capable ofrandomly incorporating the ethylene monomers and/or alpha-olefin intothe macromolecules to form the random copolymer, and a second stage of,in the further presence of the random copolymer containing activecatalyst, polymerizing a mixture of ethylene and propylene in singlestage or in plural stages to form the second ethylene-propylenecopolymer.

U.S. Pat. No. 6,342,565 teaches soft elastic fiber compositions thatinclude a crystallizable propylene copolymer and a crystalline propylenecopolymer such as isotactic polypropylene. The fibers may also include asecond crystallizable propylene copolymer. The first crystallizablepropylene copolymer is characterized by a melting point of less than a105° C. and a heat of fusion of less than 45 J/g. The crystallinepropylene copolymer may be characterized by a melting point above 110°C. and a heat of fusion greater than 60 J/g. Where a secondcrystallizable propylene copolymer is employed, it may differ from thefirst crystallizable propylene copolymer in molecular weight and/orcrystallinity content.

U.S. Pat. No. 6,635,715 describes blends of a first isotacticpolypropylene homopolymer or copolymer component with a secondalpha-olefin and propylene copolymer component, wherein the firstisotactic polypropylene component has a melting point above about 110°C., and the second copolymer has a melting point between about 25° C.and 105° C. The blends may have from 2 to 95 wt % of the first componentand from 98 to 5 wt % of the second copolymer component. In theexamples, the polypropylene used is ESCORENE 4292 (ExxonMobil ChemicalCo.), an isotactic polypropylene homopolymer having a nominal melt flowrate (MFR) of 2.0 g/10 min, and the second copolymer is illustrated byan Mw (weight-average molecular weight) of 248,900 to 318,900 and by aMooney viscosity (ML (1+4) at 125° C. according to ASTM D1646)) of from12.1 to 38.4. The blends are directed to improved mechanical propertiesof processing, increased tensile strength, elongation, and overalltoughness.

SUMMARY OF THE INVENTION

One or more embodiments of the present invention provides a method forforming a polymer blend, the method comprising: (i) charging to areactive extruder a first polymer and a second polymer to form aninitial blend, where the first polymer is a propylene-based elastomerincluding up to 35% by weight ethylene-derived units and a heat offusion, as determined according to DSC procedures according to ASTME-793, of less than 80 J/g and a melt temperature of less than 110° C.,where the second polymer is a propylene-based polymer having a melttemperature in excess of 110° C. and a heat of fusion in excess of 80J/g; (ii) after said step of charging, charging a peroxide to theinitial blend to thereby form a reactive blend; (iii) conducting thereactive blend at a flow rate through a series of barrels within theextruder; (iv) subjecting the reactive blend, in one or more barrels, tohigh shear mixing; (v) maintaining the temperature of the reactive blendat a temperature sufficient to decompose at least 50% of the peroxideand thereby form a reacted blend; (vi) restricting flow rate of thereacted blend through one or more barrels to increase the time that thereactive blend is subjected to the high shear mixing; (vii) removingcompounds from the reacted blend or the reactive blend; (viii)introducing an antioxidant to the reacted blend; (ix) increasing flowrate of the reacted blend through one or more barrels; (x) after saidstep of increasing the flow rate, passing the reacted blend through oneor more screens to thereby remove unwanted contaminates; and (xi)pelletizing the reacted blend.

Still other embodiments of the present invention provide a method forforming a polymer blend, the method comprising: (i) charging to areactive extruder a first polymer and a second polymer to form a blend,where the first polymer is a propylene-based elastomer including up to35% by weight ethylene-derived units and a heat of fusion, as determinedaccording to DSC procedures according to ASTM E-793, of less than 80 J/gand a melt temperature of less than 110° C., where the second polymer isa propylene-based polymer having a melt temperature in excess of 110° C.and a heat of fusion in excess of 80 J/g; (ii) after said step ofcharging, charging a peroxide to the blend to thereby form a reactiveblend; (iii) conducting the reactive blend at a flow rate through aseries of barrels within the extruder; (iv) subjecting the reactiveblend, in one or more barrels, to high shear mixing; (v) maintaining thetemperature of the reactive blend at a temperature of at least 165° C.for at least 5 seconds and thereby form a reacted blend; (vi)restricting flow rate of the reacted blend through one or more barrelsto increase the time that the reactive blend is subjected to the highshear mixing; (vii) removing compounds from the reacted blend or thereactive blend; (viii) introducing an antioxidant to the reacted blend;(ix) increasing flow rate of the reacted blend through one or morebarrels; (x) after said step of increasing the flow rate, passing thereacted blend through one or more screens to thereby remove unwantedcontaminates; and (xi) pelletizing the reacted blend.

Still other embodiments of the present invention provide a method forforming one or more fibers, the method comprising: (i) charging to areactive extruder a first polymer and a second polymer to form aninitial blend, where the first polymer is a propylene-based elastomerincluding up to 35% by weight ethylene-derived units and a heat offusion, as determined according to DSC procedures according to ASTME-793, of less than 80 J/g and a melt temperature of less than 110° C.,where the second polymer is a propylene-based polymer having a melttemperature in excess of 110° C. and a heat of fusion in excess of 80J/g; (ii) after said step of charging, charging a peroxide to theinitial blend to thereby form a reactive blend; (iii) conducting thereactive blend at a flow rate through a series of barrels within theextruder; (iv) subjecting the reactive blend, in one or more barrels, tohigh shear mixing; (v) maintaining the temperature of the reactive blendat a temperature sufficient to decompose at least 50% of the peroxideand thereby form a reacted blend; (vi) restricting flow rate of thereacted blend through one or more barrels to increase the time that thereactive blend is subjected to the high shear mixing; (vii) increasingflow rate of the reacted blend through one or more barrels; (viii) aftersaid step of increasing the flow rate, passing the reacted blend throughone or more screens to thereby remove unwanted contaminates; and either(ix) extruding the reacted blend through a plurality of die capillariesto form molten threads or filaments and attenuating the molten threadsor filaments in a gas stream to form meltblown fibers or (ix)introducing the reacted blend to a spinneret to form one or morefilaments and (x) quenching the filaments with air to form one or morefibers.

Still other embodiments of the present invention provide a method forforming one or more fibers, the method comprising: (i) charging to areactive extruder a first polymer and a second polymer to form a blend,where the first polymer is a propylene-based elastomer including up to35% by weight ethylene-derived units and a heat of fusion, as determinedaccording to DSC procedures according to ASTM E-793, of less than 80 J/gand a melt temperature of less than 110° C., where the second polymer isa propylene-based polymer having a melt temperature in excess of 110° C.and a heat of fusion in excess of 80 J/g; (ii) after said step ofcharging, charging a peroxide to the blend to thereby form a reactiveblend; (iii) conducting the reactive blend at a flow rate through aseries of barrels within the extruder; (iv) subjecting the reactiveblend, in one or more barrels, to high shear mixing; (v) maintaining thetemperature of the reactive blend at a temperature of at least 165° C.for at least 5 seconds and thereby form a reacted blend; (vi)restricting flow rate of the reacted blend through one or more barrelsto increase the time that the reactive blend is subjected to the highshear mixing; (vi) increasing flow rate of the reacted blend through oneor more barrels; (viii) after said step of increasing the flow rate,passing the reacted blend through one or more screens to thereby removeunwanted contaminates; and either (ix) extruding the reacted blendthrough a plurality of die capillaries to form molten threads orfilaments and attenuating the molten threads or filaments in a gasstream to form meltblown fibers or (ix) introducing the reacted blend toa spinneret to form one or more filaments and quenching the filamentswith air to form one or more fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart depicting a series of process steps according toembodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Propylene-Based Elastomer

Embodiments of the present invention employ a propylene-based elastomer,which for purposes of this specification may simply be referred to as anelastomer. Propylene-based elastomers, which may also be referred to asa propylene-based copolymers, include units (i.e., mer units) derivedfrom propylene, one or more comonomer units derived from ethylene orα-olefins including from 4 to about 20 carbon atoms, and optionally oneor more comonomer units derived from dienes. In one or more embodiments,the α-olefin comonomer units may derive from ethylene, 1-butene,1-hexene, 4-methyl-1-pentene and/or 1-octene. In one or moreembodiments, the diene comonomer units may derive from5-ethylidene-2-norbornene, 5-vinyl-2-norbornene, divinyl benzene,1,4-hexadiene, 5-methylene-2-norbornene, 1,6-octadiene,5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, 1,3-cyclopentadiene,1,4-cyclohexadiene, dicyclopentadiene, or a combination thereof. Theembodiments described below are discussed with reference to ethylene asthe α-olefin comonomer, but the embodiments are equally applicable toother propylene-based copolymers with other α-olefin comonomers.

In one or more embodiments, the propylene-based elastomers may includeat least 7 wt %, in other embodiments at least 8 wt %, in otherembodiments at least 9 wt %, and in other embodiments at least 10 wt %ethylene-derived units; in these or other embodiments, the copolymersmay include up to 25 wt %, in other embodiments up to 22 wt %, in otherembodiments up to 20 wt %, and in other embodiments up to 18 wt %ethylene-derived units, where the percentage by weight is based upon thetotal weight of the propylene-derived and α-olefin derived units. Inthese or other embodiments, the propylene-based elastomers may includeat least 75 wt %, or in other embodiments at least 78 wt %,propylene-derived units; and in these or other embodiments, thecopolymers may include up to 80 wt %, in other embodiments up to 82 wt%, in other embodiments up to 93 wt %, and in other embodiments up to 90wt % propylene-derived units, where the percentage by weight is basedupon the total weight of the propylene-derived and α-olefin derivedunits. The propylene-based elastomer may have diene derived mer units inan amount from about 0.5 wt % up to 5 wt % of the total polymer.

The ethylene content can be measured as follows for a copolymer havingan ethylene content between 5 and 40 wt % ethylene. A thin homogeneousfilm is pressed according to sub-method A of ASTM D-3900. It is thenmounted on a Perkin Elmer Spectrum 2000 infrared spectrophotometer. Afull spectrum is recorded using the following parameters: Resolution:4.0 cm⁻¹, Spectral Range: 4500 to 450 cm⁻¹. Ethylene content isdetermined by taking the ratio of the propylene band area at 1155 cm⁻¹to the ethylene band area at 722-732 cm⁻¹ (C₃/C₂=AR) and applying it tothe following equation: Wt % Ethylene=73.492−89.298X+15.637X², whereX=AR/(AR+1) and AR is the peak area ratio (1155 cm⁻¹/722-732 cm⁻¹).

The propylene-based elastomer of one or more embodiments arecharacterized by having a broad melting transition as determined bydifferential scanning calorimetry (DSC) with possible more than onemaxima points. The melting point (T_(m)) discussed here refers to thehighest temperature at which a maxima in heat absorption within therange of melting of the sample occurs.

In one or more embodiments, the T_(m) of the propylene-based elastomer(as determined by DSC) is less than 120° C., in other embodiments lessthan 100° C., in other embodiments less than 65° C., and in otherembodiments less than 60° C.

In one or more embodiments, the propylene-based elastomer may becharacterized by a heat of fusion (H_(f)), as determined by DSC. In oneor more embodiments, propylene-based elastomer may be characterized by aH_(f) that is at least 0.5 J/g, in other embodiments at least 1.0 J/g,in other embodiments at least 1.5 J/g, in other embodiments at least3.0, in other embodiments at least 4.0, in other embodiments at least6.0, and in other embodiments at least 7.0. In these or otherembodiments, propylene-based elastomer may be characterized by a H_(f)that of less than 80 J/g, in other embodiments less than 75 J/g, inother embodiments less than 65 J/g, in other embodiments less than 55J/g, in other embodiments less than 50 J/g, in other embodiments lessthan 45 J/g, and in other embodiments from about 30 to about 50 J/g.Crystallinity may be determined by dividing the heat of fusion of asample by the heat of fusion of a 100% crystalline polymer, which isassumed to be 189 J/g for isotactic polypropylene.

As used within this specification, DSC procedures for determining T_(m)and H_(f) include the following. The polymer is pressed at a temperatureof from about 200° C. to about 230° C. in a heated press, and theresulting polymer sheet is hung, under ambient conditions, in the air tocool. About 6 to 10 mg of the polymer sheet is removed with a punch die.This 6 to 10 mg sample is annealed at room temperature for about 80 to100 hours. At the end of this period, the sample is placed in aDifferential Scanning Calorimeter (Perkin Elmer 7 Pyris One ThermalAnalysis System) and cooled to about −50° C. to about −70° C. The sampleis heated at 10° C./min to attain a final temperature of about 200° C.The sample is kept at 200° C. for 5 minutes and a second cool-heat cycleis performed. Events from both cycles are recorded. The thermal outputis recorded as the area under the melting peak of the sample, whichtypically occurs between about 0° C. and about 200° C. It is measured inJoules and is a measure of the H_(f) of the polymer. The T_(m) discussedhere refers to the highest temperature at which a maxima in heatabsorption within the range of melting of the sample occurs. This mightalso be typically the temperature of the greatest heat absorption withinthe range of melting of the sample.

The propylene-based elastomer can have a triad tacticity of threepropylene units, as measured by ¹³C NMR, of 75% or greater, 80% orgreater, 82% or greater, 85% or greater, or 90% or greater. In one ormore embodiments, the triad tacticity ranges include from about 50 toabout 99%, in other embodiments from about 60 to about 99%, in otherembodiments from about 75 to about 99%, in other embodiments from about80 to about 99%, and in other embodiments from about 60 to about 97%.Triad tacticity is determined by the methods described in U.S. Pat. No.7,232,871.

In one or more embodiments, the propylene-based elastomer has a narrowcompositional distribution (CD). This intermolecular compositiondistribution of the copolymer can be determined by thermal fractionationin a solvent such as hexane or heptane, as follows. Approximately 75% byweight and more preferably 85% by weight of the polymer is isolated asone or two adjacent soluble fractions with the balance of the copolymerin immediately preceding or succeeding fractions. In order for thecopolymer to have a narrow compositional distribution as discussedabove, each of the isolated fractions will generally have a composition(wt % ethylene content) with a difference of no greater than 20 wt %(relative) or in other embodiments no greater than 10 wt % (relative)from the average wt % ethylene content of the entire second polymercomponent.

In general, the propylene-based elastomers can be synthesized to have abroad range of molecular weights and/or be characterized by a broadrange of MFR. For example, the propylene-based elastomers can have aMFR, as measured according to the ASTM D-1238, 2.16 kg weight @230° C.,of at least 1.0 dg/min, in other embodiments at least 0.5 dg/min, and inother embodiments at least 1.5 dg/min. In these or other embodiments,the MFR may be less than 180 dg/min, and in other embodiments less than150 dg/min.

In one or more embodiments, the propylene-based elastomer can have aweight average molecular weight (M_(w)) of about 5 to about 5,000kg/mole, in other embodiments a M_(w) of about 10 to about 1,000kg/mole, in other embodiments a M_(w) of about 20 to about 500 kg/moleand in other embodiments a M_(w) of about 50 to about 400 kg/mole.

In one or more embodiments, the propylene-based elastomer can have anumber average molecular weight (M_(n)) of about 2.5 to about 2,500kg/mole, in other embodiments a M_(n) of about 5 to about 500 kg/mole,in other embodiments a M_(n) of about 10 to about 250 kg/mole, and inother embodiments a M_(n) of about 25 to about 200 kg/mole.

In one or more embodiments, the molecular weight distribution index(MWD=(M_(w)/M_(n))) of the propylene-based elastomer may be about 1 toabout 40, in other embodiments about 1 to about 5, in other embodimentsabout 1.8 to about 5, and in other embodiments about 1.8 to about 3.

Techniques for determining the molecular weight (M_(n), M_(w)) andmolecular weight distribution (MWD) may be found in U.S. Pat. No.4,540,753 (Cozewith, Ju and Ver Strate) (which is incorporated by thereference herein for purposes of U.S. practices) and the referencescited therein and in Macromolecules, 1988, Volume 21, pp. 3360-3371 (VerStrate et al.), which is herein incorporated by reference for purposesof U.S. practices, and references cited therein. For example, molecularweight may be determined by size exclusion chromatography (SEC) by usinga Waters 150 gel permeation chromatograph equipped with the differentialrefractive index detector and calibrated using polystyrene standards.

The propylene-based elastomers employed in the present invention may beprepared by employing synthetic techniques known in the art forpreparing propylene-based elastomers having the foregoingcharacteristics. Reference can be made to U.S. Pat. Nos. 6,525,157,6,982,310, 6,992,158, 6,992,159, and 6,992,160. Propylene-basedelastomers are commercially available, for example, under the trade nameVISTAMAXX (ExxonMobil Chemical Co.).

Propylene-Based Thermoplastic Polymer

Embodiments of the present invention employ a propylene-basedthermoplastic resin, which for purposes of this specification may simplybe referred to as a resin or thermoplastic resin. Propylene-basedthermoplastic resins, which may also be referred to as propylene-basedthermoplastic polymers, include those polymers that primarily compriseunits deriving from the polymerization of propylene. In certainembodiments, at least 98% of the units of the propylene-basedthermoplastic polymer derive from the polymerization of propylene. Inparticular embodiments, these polymers include homopolymers ofpropylene.

In certain embodiments, the propylene-based thermoplastic polymers mayalso include units deriving from the polymerization of ethylene and/orα-olefins such as 1-butene, 1-hexene, 1-octene, 2-methyl-1-propene,3-methyl-1-pentene, 4-methyl-1-pentene, 5-methyl-1-hexene, and mixturesthereof. Specifically included are the reactor, impact, and randomcopolymers of propylene with ethylene or the higher α-olefins, describedabove, or with C₁₀-C₂₀ diolefins.

In one or more embodiments, the propylene-based thermoplastic polymerscan have a T_(m) that is greater than 120° C., in other embodimentsgreater than 155° C., and in other embodiments greater than 160° C. Inthese or other embodiments, the propylene-based thermoplastic polymerscan have a T_(m) that is less than 180° C., in other embodiments lessthan 170° C., and in other embodiments less than 165° C.

In one or more embodiments, the propylene-based thermoplastic polymersmay be characterized by an H_(f) that is equal to or greater than 80J/g, in other embodiments greater than 100 J/g, in other embodimentsgreater than 125 J/g, and in other embodiments greater than 140 J/g asmeasured by DSC.

In one or more embodiments, propylene-based thermoplastic polymers mayinclude crystalline and semi-crystalline polymers. In one or moreembodiments, these polymers may be characterized by a crystallinity ofat least 40% by weight, in other embodiments at least 55% by weight, inother embodiments at least 65%, and in other embodiments at least 70% byweight as determined by DSC. Crystallinity may be determined by dividingthe heat of fusion of a sample by the heat of fusion of a 100%crystalline polymer, which is assumed to be 189 J/g for isotacticpolypropylene.

In general, the propylene-based thermoplastic polymers may besynthesized having a broad range of molecular weight and/or becharacterized by a broad range of MFR. For example, the propylene-basedthermoplastic polymers can have a MFR of at least 2 dg/min, in otherembodiments at least 4 dg/min, in other embodiments at least 6 dg/min,and in other embodiments at least, where the MFR is measured accordingto ASTM D-1238, 2.16 kg @230° C. In these or other embodiments, thepropylene-based thermoplastic polymer can have an MFR of less than 2,000dg/min, in other embodiments less than 400 dg/min, in other embodimentsless than 250 dg/min, in other embodiments less than 100 dg/min, and inother embodiments less than 50 dg/min, where the MFR is measuredaccording to ASTM D-1238, 2.16 kg @230° C.

In one or more embodiments, the propylene-based thermoplastic polymersmay be characterized by an M_(w) of from about 50 to about 2,000kg/mole, and in other embodiments from about 100 to about 600 kg/mole.They may also be characterized by a M_(n) of about 25 to about 1,000kg/mole, and in other embodiments about 50 to about 300 kg/mole, asmeasured by GPC with polystyrene standards.

The propylene-based thermoplastic polymers may be synthesized by usingan appropriate polymerization technique known in the art such as,slurry, gas phase or solution but not limited to, using catalyst systemssuch as conventional Ziegler-Natta or single-site organometalliccatalysts like metallocenes, or any organometallic compound capable ofpolymerizing olefin.

In one embodiment, the propylene-based thermoplastic polymers includehighly crystalline polypropylene such as isotactic polypropylene. Thispolypropylene can have a density of from about 0.85 to about 0.91 g/cc,with the largely isotactic polypropylene having a density of from about0.90 to about 0.91 g/cc.

Peroxide

Embodiments of the present invention employ a peroxide. In one or moreembodiments, useful peroxides include those that can break down (i.e.size or sever) the polymeric chains and alter the molecular weightdistribution. Various peroxides known in the art can be used including,but not limited to, dialkyl peroxides. Examples include2,5-dimethyl-2,5-di-(t-butylperoxyl)hexane and dicumyl peroxide. Usefulperoxides are available under the name LUPEROX 101 (Arkema).

Other Ingredients

The blends of this invention may also comprise other ingredients. Forexample the blends of this invention may comprise nucleating agents,which can be present at 50 to 4000 ppm based on total polymer in theblend composition. Nucleating agents include, for example, sodiumbenzoate and talc. Also, other nucleating agents may also be employedsuch as Ziegler-Natta olefin product or other highly crystallinepolymer. Nucleating agents include HYPERFORM such as HPN-68 and Milladadditives (e.g., Millad 3988) (Milliken Chemicals, Spartanburg, S.C.)and organophosphates like NA-11 and NA-21 (Amfine Chemicals, Allendale,N.J.).

Further, a variety of additives may be incorporated into the embodimentsdescribed above used to make the blends, fibers, and fabrics for variouspurposes. Other additives include, for example, stabilizers,antioxidants, fillers, and slip aids. Primary and secondary antioxidantsinclude, for example, hindered phenols, hindered amines, and phosphites.Other additives such as dispersing agents, for example, Acrowax C, canalso be included. Catalyst deactivators may also be used including, forexample, calcium stearate, hydrotalcite, and calcium oxide, and/or otheracid neutralizers known in the art.

In one or more embodiments, useful slip aids include those compounds ormolecules that are incompatible with the polymeric matrix of the fibers(i.e., the propylene-based elastomers and/or propylene-basedthermoplastic resins and/or feel modifiers) and therefore migrate to thesurface of the fiber. In these or other embodiments, useful slip aidsare characterized by relatively low molecular weight, which canfacilitate migration to the surface. Types of slip aids include fattyacid amides as disclosed in Handbook of Antiblocking, Release and SlipAdditives, George Wypych, Page 23. Examples of fatty acid amides includebehenamide, erucamide, N-(2-hdriethyl)erucamide, lauramide,N,N′-ethylene-bis-oleamide, N,N′-ethylene bisstearmide, oleamide, oleylpalmitamide, stearyl is erucamide, tallow amide, and mixtures thereof

Other additives include, for example, fire/flame retardants,plasticizers, vulcanizing or curative agents, vulcanizing or curativeaccelerators, cure retarders, processing aids, and the like. Theaforementioned additives may also include fillers and/or reinforcingmaterials, either added independently or incorporated into an additive.Examples include carbon black, clay, talc, calcium carbonate, mica,silica, silicate, combinations thereof, and the like. Other additiveswhich may be employed to enhance properties include antiblocking agentsor lubricants.

In yet other embodiments, isoparaffins, polyalphaolefins, polybutenes,or a mixture of two or more thereof may also be added to thecompositions of the invention. Polyalphaolefins may include thosedescribed in WO 2004/014998. These polyalphaolefins may be added inamounts such as about 0.5 to about 40% by weight, in other embodimentsfrom about 1 to about 20% weight, and in other embodiments from about 2to about 10% by weight. In particular embodiments, highly purifiedparaffinic oils may be used. These highly purified paraffinic oils mayinclude greater than 70%, and in other embodiments greater than 80%,paraffin content. Useful paraffinic oils are disclosed in U.S.Publication Nos. 2006/0008643, 2006/0247332, 2006/0247331, and2006/135699, which are incorporated herein by reference. In one or moreembodiments, the paraffinic oils may advantageously be used as a carrieror a slurry medium for delivering one or more ingredients to theextruder. For example, paraffinic oils may be employed to carry theperoxide to the extruder.

Formation of Blend

Embodiments of the present invention are directed toward methods forpreparing polymer blends. These methods uniquely and unexpectedlyproduce pellets of the polymer blend that have technologically usefulproperties including advantageous melt flow, mechanical and dynamicproperties, and handling characteristics.

One or more embodiments of the present invention can be described withreference to FIG. 1. A blending process 10 is shown where apropylene-based elastomer is introduced with a propylene-basedthermoplastic resin within a barrel location 12 within a reactionextruder (the entirety of which is not shown) to form an initial blend.The elastomer and the resin can be added via a feed throat using precisemetering feeders such as loss-in-weight or volumetric screw feeder or abelt feeder. The elastomer and resin can be added separately at the samelocation or at different locations along the extruder. When added atseparate locations, the constituents may be pre-masticated orplasticized using a side-extruder.

Those skilled in the art will also appreciate that the introduction ofthe elastomer and the resin can also occur outside of the extruder in ablender such as a ribbon blender or a tumbling blender, and the blendcan be charged to the extruder without departing from the invention. Theprocess may also be carried out in multiple staged extrusions—forinstance, masterbatches of one or more of the polymers may be preparedin the first stage, followed by reactive extrusion in a subsequentstage. Masterbatches include dispersions of one or more of the polymericingredients, peroxides, anti-oxidants, UV and other stabilizers, andplasticizers. Masterbatches may be “dry mixes”, by which is meant, asimple physical admixture that has not been “fully-wetted” or dispersedat the molecular level. For example, a “dry mix” is obtained when twoingredients are simply tumbled together in a tumbling mill or in aribbon blender. A “dispersion” is obtained when the ingredients aremechanically worked and/or heated such that one or more of theingredients melts and coats the other ingredient and/or disperses intothe other ingredients.

The amount of propylene-based elastomer introduced with propylene-basedthermoplastic resin can vary depending upon the properties that areultimately desired. In one or more embodiments, the blend includes atleast 50 parts by weight, in other embodiments at least 60 parts byweight, in other embodiments at least 70 parts by weight and in otherembodiments at least 80 parts by weight of the propylene-based elastomerbased upon the total weight of the propylene-based elastomer and thepropylene-based thermoplastic resin. In these or other embodiments, theblend includes less than 98 parts by weight, in other embodiments lessthan 95 parts by weight, and in other embodiments less than 90 parts byweight of the propylene-based elastomer based upon the total weight ofthe propylene-based elastomer and the propylene-based thermoplasticresin.

In one or more embodiments, the blend includes at least 2 parts byweight, in other embodiments at least 5 parts by weight, in otherembodiments at least 10 parts by weight, and in other embodiments atleast 12 parts by weight of the propylene-based thermoplastic resinbased upon the total weight of the propylene-based elastomer and thepropylene-based thermoplastic resin. In these or other embodiments, theblend includes less than 50 parts by weight, in other embodiments lessthan 30 parts by weight, and in other embodiments less than 20 parts byweight of the propylene-based thermoplastic resin based upon the totalweight of the propylene-based elastomer and the propylene-basedthermoplastic resin.

In one or more embodiments, the reaction extruder includes thoseextruders that can perform reactive extrusion. These extruders includethose continuous mixing extruders known in the art such as single-screwextruders, co-rotating intermeshing twin-screw extruders, andcounter-rotating non-intermeshing twin-screw extruders, as well as othermulti-screw extruders. These reaction extruders generally include aseries of barrels that when connected form a passageway or conduitthrough which polymer may be conducted. The passageway may include twoor more screws that are adapted with a plurality of elements that impactthe progression of the polymer through each barrel. For example, theelements may primarily convey material though the barrels, they mayserve to mix and masticate the material within the barrel, and/or theymay primarily serve to restrict flow or induce back-mixing within one ormore barrels. Once armed with a desired mixing sequence and strategy,those skilled in the art will be able to readily adapt the variouselements of the various screws to achieve the desired sequence orstrategy outlined herein.

With reference again to FIG. 1, the initial blend is then conveyed to abarrel location 14 where a peroxide is introduced to the initial blendto thereby form a reactive blend. The peroxide may be added as a liquidor a powder using separate feeders. Alternatively, the peroxide may bepreblended with the propylene-based elastomer and/or the propylene-basedthermoplastic resin, or with other ingredients used in the process, andthen charged to the extruder.

The reactive blend is then conveyed to a zone of high-shear mixing 16,where the reactive blend undergoes intense mixing and masticating. Thiszone may include one or more barrels wherein the rotating shafts orscrews of the extruder are equipped with high-shear kneading elements,as well as optional reverse and back-mixing elements that increase theresidence time of the reactive blend within high-shear mixing zone 16.The combination of the shaft speed and the high-shear mixing from thekneading elements elevates the temperature of the reactive blend. In oneor more embodiments, the temperature of the blend may also be increasedby the use of external heating sources.

It is believed that the peroxide decomposes on heating and generatesfree radicals that react with the propylene-based elastomer and/or thepropylene-based thermoplastic resin. It is also believed that peroxidesaffect the propylene-based elastomer and the propylene-basedthermoplastic resin to different extents and by different mechanisms.Namely, it is believed that peroxide, under the appropriate conditions,primarily serves to sever or crack the propylene-based thermoplasticresin (a process known as vis-breaking) and thereby reduce the molecularweight. The peroxide is believed to also impact the methylene segmentsof the propylene-based elastomer to branch or crosslink the chains andthereby increase the molecular weight while lowering melt flow rate.Also, it is believed that free-radical chain ends of the propylene-basedelastomer and the propylene-based thermoplastic resin may graft or reactwith each other and scramble chain segments, thereby resulting inconstituents with block segments of each respective polymer ingredient(i.e., a block of the propylene-based elastomer and a block of thepropylene-based thermoplastic resin).

It has unexpectedly been discovered that by maintaining a highertemperature and sufficient residence time at this higher temperatureand/or high-shear mixing, advantageous product results. This unexpecteddiscovery may stem from a difference in the way that the peroxideinteracts or reacts with propylene-based elastomer and thepropylene-based thermoplastic resin. That is, the peroxide may reactwith the propylene-based thermoplastic resin more quickly, under lessershear, and at lower temperatures than the reaction with thepropylene-based elastomer, and therefore the advantages associated withthe reaction with the propylene-based elastomer can only be achievedwith higher shear mixing, higher temperature, and/or longer residencetime. Thus, while conventional practice may have sought to extract heatfrom the blend via means such as water cooling and/or use lessaggressive mixing profiles, practice of the present invention includesmaintaining conditions within high-shear mixing zone 16 so as to achievesufficient peroxide decomposition to achieve desired materialproperties.

In one or more embodiments, the temperature of the reactive blend ismaintained within high-shear mixing zone 16 at a temperature of at least195° C., in other embodiments at least 205° C., in other embodiments atleast 215° C., and in other embodiments at least 220° C. In these orother embodiments, the temperature is maintained below the decompositiontemperature of the polymers or that temperature at which a deleteriousamount of gel will be produced. In one or more embodiments, thetemperature of the blend is maintained below 300° C., in otherembodiments below 270° C., and in other embodiments below 250° C.

In one or more embodiments, the residence time that the reactive blendis maintained at the specified elevated temperatures may be at least 5seconds, in other embodiments at least 10 seconds, in other embodimentsat least 15 seconds, in other embodiments at least 20 seconds, in otherembodiments at least 25 seconds, in other embodiments at least 30seconds, and in other embodiments at least 35 seconds. In these or otherembodiments, the residence time that reactive blend is maintained at thespecified elevated temperatures may be less than 90 seconds, in otherembodiments less than 80 seconds, in other embodiments less than 70seconds, in other embodiments less than 60 seconds, and in otherembodiment less than 50 seconds.

In view of the foregoing, those skilled in the art will also appreciatethat the amount of peroxide employed is another variable that can bemanipulated to achieve the desired reaction. In other words, thereaction sought between the polymers within the blend and the peroxidemay be contingent upon the temperature, the residence time, and theconcentration of the peroxide present. In one or more embodiments, theamount of peroxide introduced with the blend may be at least 500 ppm(weight), in other embodiments at least 1000 ppm, in other embodimentsat least 1500 ppm, in other embodiments at least 2000 ppm, in otherembodiments at least 2500 ppm, in other embodiments at least 3000 ppm,in other embodiments at least 3500 ppm, in other embodiments at least4000 ppm, in other embodiments at least 4500 ppm, and in otherembodiments at least 5000 ppm peroxide based upon the weight of thepropylene-based elastomer and the propylene-based thermoplastic resincombined. In these or other embodiments, the amount of peroxideintroduced with the blend may be less than 10,000 ppm, in otherembodiments less than 8000 ppm, in other embodiments less than 6000 ppmperoxide, in other embodiments less than 5000 ppm, in other embodimentsless than 4000 ppm, and in other embodiments less than 3000 ppm basedupon the total parts by weight of the propylene-based elastomer and thepropylene-based thermoplastic resin.

In other embodiments, the conditions within high-shear mixing zone 16can be described with reference to the decomposition of the peroxideintroduced to the mixture. In one or more embodiments, the conditionswithin high-shear mixing zone 16, including the temperature andresidence time, are controlled to achieve at least 50%, in otherembodiments at least 60%, in other embodiments at least 70%, in otherembodiments at least 80%, in other embodiments at least 90%, in otherembodiments at least 95%, and in other embodiments at least 99%decomposition (i.e., conversion) of the peroxide that is introduced tothe blend. This conversion may occur entirely within high-shear mixingzone 16 or the conditions within high-shear mixing zone 16 maycontrolled to allow the desired conversion in downstream zones orbarrels.

As shown in FIG. 1, volatile compounds present within high-shear mixingzone 16 can optionally be removed from high-shear mixing zone 16 thoughan outlet 18, which may include a vent section within the extruder. Avacuum pump (not specifically shown) can be used to improve thedevolatilization and removal of volatiles.

In addition to outlet 18 or in lieu of outlet 18, volatile compounds canoptionally be removed from a conveying zone 20, which will be describedherein below, via an outlet 22. Outlet 22, like outlet 8, may include avent section within the extruder and a vacuum pump to improve thedevolatilization and removal of volatiles.

It is believed that the free radical decomposition of the peroxide mayproduce volatile gases such as methane and hydrogen, as well asoxygen-bearing compounds such as, but not limited to, acetone, alcoholssuch as t-butyl alcohols, and aldehydes such as formaldehyde. Moisturepresent in the raw material feeds may also generate water vapor. Thesevapors and gases, including entrapped air or nitrogen that enters theextruder along with the raw material feeds can be removed as volatilecompounds. It has unexpectedly been discovered that the removal of thesevolatile compounds has a positive impact on the subsequent pelletizationstep, which will be described herein below.

With reference again to FIG. 1, the reactive blend is conveyed away fromhigh-shear mixing zone 16 via conveying zone 20 where the reactive blendmay complete its conversion from a reactive blend to a reacted blend.Also, the reacted blend may be allowed to cool within conveying zone 20.Those skilled in the art will appreciate that the temperature of thereacted blend should be maintained at temperatures sufficient tomaintain adequate flow of the blend, but the temperature need not, andis desirably not, maintained at the high temperatures maintainedupstream where peroxide decomposition and reaction was sought.

In one or more embodiments, an antioxidant can be introduced with thereacted blend. For example, as shown in FIG. 1, an antioxidant can beadded via a feeder 24 as the reacted blend is conveyed away fromhigh-shear mixing zone 16. In one or more embodiments, one or moreantioxidants are introduced together with a carrier material such as aplasticizer, an extender oil, or other low molecular weight material. Inone or more embodiments, the antioxidant together with the low viscositymaterial may be injected into a barrel of the extruder as a slurry.

In one or more embodiments, the antioxidant is an alkylated phenol suchas 2,6-di-tert-butylphenol (2,6-DTBP), a butylated hydroxyl toluene suchas 2,6-bis(1,1-dimethylethyl)-4-methylphenol), and/or a phosphite suchas tris(2,4-di-(tert)-butylphenyl)phosphite. The low molecular weightcompounds that may be introduced with the antioxidant include paraffinicoils such as highly purified paraffinic oils and disclosed above. Anexample of a useful oil is that available under the trade nameSPECTRASYN (ExxonMobil Chemical Co.).

In one or more embodiments, after the optional introduction of theantioxidant or other optional materials, which may be introduced to theblend within the extruder, the reacted blend may enter a pressureincreasing zone 26, which serves to increase the force and/or flow rateof the reacted blend and thereby facilitate transfer of the reactedblend through a die plate (not shown). Pressure increasing zone 26 mayinclude extruder screw segments that are designed to generate adequateor increased pressure. In other embodiments, pressure increasing zone 26may include a gear pump. The use of a gear pump advantageously helpsminimize process upsets and isolate the extruder from the pressurechanges associated with downstream treatment, such as screening, whichwill be described below. Thus, it should be appreciated that pressureincreasing zone 26 may be located within one or more barrels of theextruder or may be external to the extruder.

Pressure-increasing zone 26 may also serve to facilitate passing thereacted blend through one or more screens 28, which can be used toremove contaminates such as metal chips, polymeric gels, and/or unmeltedpellets of raw material. This step of screening may take place withinthe extruder or after or upon exit of the reacted blend from theextruder. In particular embodiments, screens are installed between theextruder outlet and a die plate.

In one or more embodiments, the reacted blend is pelletized orgranulated at pelletizer 30. In one or more embodiments, the reactedproduct, as a hot extrudate, is passed through a specially constructeddie plate that shapes the product into a ribbon that is drawn out usinga rotating drum. The drum is water cooled and/or placed in a watertrough for quenching the hot extrudate. The ribbon is then cut or groundinto small chips that may range in size from about 0.5 mm to about 20mm. The width of the die hole determines the thickness of the pellets.

In other embodiments, a die plate with multiple holes, which may rangein width from about 0.5 mm to about 20 mm, is employed. The reactedblend, which is generally in the form of molten stands or ropes, is cutinto little pellets that are typically cylindrical in shape. The lengthof the pellets is can be altered by manipulating the speed of the bladeson the cutter or by changing the distance between blades.

In one or more embodiments, an underwater pelletizer is employed. Thereacted blend, in the form of a molten extrudate, is forced through adie plate containing one or more die-holes. The die plate may be heatedand/or cooled to adjust the viscosity of the blend to make it moresuitable for pelletization. Electric heaters may be used to control thedie temperature. Alternately, tempered oil, water, steam and/or otherheater transfer oils may be used to regulate the die temperature. Theextrudate flowing out of the die holes can be quenched using a rapidlyflowing stream of water in the water chamber of the underwaterpelletizer. In particular embodiments, a diverter is used to enhance thewater flow at the die plate and improve pelletization. In these or otherembodiments, the number of blades on the pelletizer hub is varied toobtain the desired pellet size. In these or other embodiments, therotary speed of the pelletizer knives adjusted to obtain desiredpellets.

In particular embodiments, the water is treated with (or includes) ananti-block agent or dispersant. These agents assist in keeping thepellets from agglomerating. In particular embodiments, calcium stearatepowder is dispersed in the pelletizer water to minimize agglomeration.

In other embodiments, the water in which the extrudate is pelletized ischilled by using a refrigeration source. In one or more embodiments, thetemperature of the water is chilled to temperatures below 50° C., inother embodiments below 40° C., in other embodiments below 30° C., inother embodiments below 20° C., and in other embodiments below 10° C.

The pellets may then be carried in a stream of water to a spin dryer,shaker screen, vibrating conveyor, fluidized bed dryer, or other dryingapparatus where the water can be screened out using centrifugal orgravitational forces. The pellets may then be screened to removeoversize pellets and fines. A fluidized bed dryer may be used to furtherenhance the drying of the pellets. Pellets of the desired size range maythen be pneumatically conveyed to holding bins or silos, which may bedesigned to provide appropriate residence time and/or blending toprovide a uniform size for packaging. The product may then be packagedin super sacks or cardboard boxes. Alternatively, the product may beloaded on to railcars, totes, or bulk bins for transportation. Or, theproduct may be packaged in bags using manual or automated baggingmachines or “form-fill-and-seal” bagging equipment.

In one or more embodiments, the reacted blend may be supplied directlyto melt spinning or melt blowing apparatuses. By supplied directly, itis meant that the reacted blend is supplied to the melt spinning or meltblowing apparatus without first being pelletized. Thus, in one or moreembodiments the reacted blend is not pelletized or solidified beforebeing directed to a melt spinning or melt blowing apparatus.

In one or more embodiments, the reacted blend may be meltblown intovarious fiber and nonwoven compositions (e.g., fabrics) as describedbelow. For example, in a meltblown process, the reacted blend may passthrough the reactive extruder outlet to a meltblowing apparatus, wherethe reactive blend is extruded through a plurality of fine, usuallycircular, die capillaries as molten threads or filaments into highvelocity, usually hot, gas streams which attenuate the filaments of theresulting molten thermoplastic material to reduce their diameter.Thereafter, the meltblown fibers are carried by the high velocity gasstream and are deposited on a collected surface to form a web ornonwoven fabric of randomly dispersed meltblown fibers. Meltblowingprocesses are generally described in, for example, U.S. Pat. Nos.3,849,241 and 6,268,203. The meltblown process may utilize an extrusionsystem having a relatively high throughput, in excess of 0.3 grams perhole per minute (“ghm”), or in excess of 0.4 ghm, or in excess of 0.5ghm, or in excess of 0.6 ghm, or in excess of 0.7 ghm.

In one or more embodiments, the reacted blend may be spunbond intovarious fiber and nonwoven compositions (e.g., fabrics) as describedbelow. For example, the reactive blend may pass through the reactiveextruder outlet to a spinneret where the blend is fiberized as passedthrough fine openings arranged in one or more rows in the spinneret,forming a curtain of filaments. The filaments are usually quenched withair at a low temperature, drawn, usually pneumatically, and deposited ona moving mat, belt, or “forming wire” to form the nonwoven composition.See, for example, the spunbond processes described in U.S. Pat. Nos.4,340,563; 3,692,618; 3,802,817; 3,338,992; 3,341,394; 3,502,763; andU.S. Pat. No. 3,542,615. The term spunbond as used herein is meant toinclude spunlace processes, in which the filaments are entangled to forma web using high-speed jets of water (known as “hydroentanglement”). Thespunbond fibers may have a diameter in the range of from about 10 toabout 50 microns, depending on the process conditions and the desiredend use for the fabrics to be produced from such fibers. Changes in thequench air temperature and pneumatic draw process may be used to alterthe fiber diametner.

Product Characteristics

In one more embodiments, the polymer blend resulting from the process ofthis invention are characterized by one or more advantageous properties.In one or more embodiments, the blend is characterized by a melt flowrate, as determined by ASTM D-1238, 2.16 kg weight @230° C., of at least60 dg/min, in other embodiments at least 80 dg/min, in other embodimentsat least 100 dg/min, in other embodiments at least 150 dg/min, in otherembodiments at least 170 dg/min, and in other embodiments at least 190dg/min. In these or other embodiments, the melt flow rate of the blendmay be less than 800 dg/min, in other embodiments less than 500, inother embodiments less than 400, in other embodiments less than 300, inother embodiments less than 250 dg/min, in other embodiments less than230 dg/min, and in other embodiments less than 210 dg/min.

Industrial Applicability

The polymer blend resulting from the process of this invention may beemployed to prepare non-woven fabrics. The formation of non-wovenfabrics from the foregoing compositions may include manufacture offibers by extrusion followed by weaving or bonding. The extrusionprocess may be accompanied by mechanical or aerodynamic drawing of thefibers. The fiber and fabrics of the present invention may bemanufactured by any technique and/or equipment known in the art, many ofwhich are well known. For example, spunbond non-woven fabrics may beproduced by spunbond non-woven production lines produced by ReifenhauserGmbH & Co., of Troisdorf, Germany. The Reifenhasuer system utilizes aslot drawing technique as revealed in U.S. Pat. No. 4,820,142.

In one or more embodiments, fibers may be produced by continuousfilament, bulked continuous filament, or staple fiber-formationtechniques. For example, the polymer melt may be extruded through theholes in the die (spinneret), which may, for example be, between, 0.3 mmto 0.8 mm in diameter. Low melt viscosity of the polymer may be achievedthrough the use of high melt temperature (e.g., 230° C. to 280° C.) andhigh melt flow rates (e.g., 15 g/10 min to 40 g/10 min) of the polymersused. A relatively large extruder may be equipped with a manifold todistribute a high output of molten polymer to a bank of eight to twentyspinnerets. Each spinhead may be equipped with a separate gear pump toregulate output through that spinhead; a filter pack, supported by a“breaker plate;” and the spinneret plate within the head. The number ofholes in the spinneret plate determines the number of filaments in a yamand varies considerably with the different yarn constructions, but it istypically in the range of 50 to 250. The holes can be grouped intoround, annular, or rectangular patterns to assist in good distributionof the quench air flow.

Continuous Filament

Continuous filament yarns can range from 40 denier to 2,000 denier(denier=number of grams/9000 yd). Filaments can range from 1 to 20denier per filament (dpf), although larger ranges are contemplated.Spinning speeds may include 800 m/min to 1500 m/min (2500 ft/min to 5000ft/min). An exemplary method would proceed as follows. The filaments aredrawn at draw ratios of 3:1 or more (one- or two-stage draw) and woundonto a package. Two-stage drawing allows higher draw ratios to beachieved. Winding speeds are 2,000 m/min to 3,500 m/min (6,600 ft/min to11,500 ft/min) Spinning speeds in excess of 900 m/min (3000 ft/min) mayrequire a narrow molecular weight distribution to get the bestspinnability with the finer filaments. Resins with a minimum MFR of 5and a narrow molecular weight distributor, with a polydispersity index(PI) under 2.8 for example. In slower spinning processes, or in heavierdenier filaments, a 16-MFR reactor grade product is may be moreappropriate.

Partially Oriented Yarn (POY)

Partially oriented yarn (POY) is the fiber produced directly from fiberspinning without solid state drawing (as continuous filament mentionedabove). The orientation of the molecules in the fiber is done only inthe melt state just after the molten polymer leaves the spinneret. Oncethe fiber is solidified, no drawing of the fiber takes place and thefiber is wounded up into a package. The POY yarn (as opposed to fullyoriented yarn, or FOY, which has gone through solid state orientationand has a higher tensile strength and lower elongation) tends to have ahigher elongation and lower tenacity.

Bulked Continuous Filament

Bulked continuous filament fabrication processes fall into two basictypes, one-step and two steps. For example, in a two-step process, anundrawn yarn is spun at less than 1,000 m/min (3,300 ft/min), usually750 m/min, and placed on a package. The yarn is drawn (usually in twostages) and “bulked” on a machine called a texturizer. Winding anddrawing speeds are limited by the bulking or texturizing device to 2,500m/min (8,200 ft/min) or less. As in the two-step CF process, secondarycrystallization requires prompt draw texturizing. Common processesinclude one-step spin/draw/text (SDT) processes. This process mayprovide better economics, efficiency and quality than the two-stepprocess. They are similar to the one-step CF process, except that thebulking device is in-line. Bulk or texture may change yarn appearance,separating filaments and adding enough gentle bends and folds to makethe yarn appear fatter (bulkier).

Staple Fiber

Fiber fabrication processes include two processes: traditional andcompact spinning The traditional process typically involves two steps:i) producing, applying finish, and winding followed by ii) drawing, asecondary finish application, crimping, and cutting into staple.Filaments can range, for example, from 1.5 dpf to >70 dpf, depending onthe application. Staple length can be as short as 7 mm or as long as 200mm (0.25 in. to 8 in.) to suit the application. For many applications,the fibers are crimped. Crimping is accomplished by over-feeding the towinto a steam-heated stuffer box with a pair of nip rolls. The over-feedfolds the tow in the box, forming bends or crimps in the filaments.These bends may be heat-set by steam injected into the box. The MW, MWD,and isotactic content of the resin can affect crimp stability,amplitude, and ease of crimping.

Melt Blown Fabrics

Melt blown fabrics may refer to webs of fine filaments having fiberdiameter in the range of 20 to 0.1 microns. Fiber diameters of meltblown fibers may be in the range of 1 to 10 microns, or in otherembodiments from 1 to about 5 microns. The non-woven webs formed bythese fine fiber diameters have very small pore sizes and therefore mayhave excellent barrier properties. For example, in the melt blownprocess, the extruder melts the polymer and delivers it to a meteringmelt pump. The melt pump delivers the molten polymer at a steady outputrate to the special melt blowing die. As the molten polymer exits thedie, they are contacted by high temperature, high velocity air (calledprocess or primary air). This air rapidly draws and, in combination withthe quench air, solidifies the filaments. The entire fiber formingprocess typically takes place within several inches of the die. Diedesign can be important to producing a quality product efficiently. Thefabric is formed by blowing the filaments directly onto a porous formingbelt, typically 200 mm to 400 mm (8 in. to 15 in.) from the spinnerets.A larger forming distance may be used for heavier basis weight, higherloft product. Melt blowing may require very high melt flow rate resinssuch as those greater than 200 g/10 min, to obtain the finest possiblefibers, although resin MFR as low as 20 g/10 min can be used at a higherprocessing temperature in other embodiments.

Spunbonded Fabric

Spunbond or spunbonded fibers include fibers produced, for example, bythe extrusion of molten polymer from either a large spinneret havingseveral thousand holes or with banks of smaller spinnerets, for example,containing as few as 40 holes. After exiting the spinneret, the moltenfibers are quenched by a cross-flow air quench system, then pulled awayfrom the spinneret and attenuated (drawn) by high speed air. There aregenerally two methods of air attenuation, both of which use the venturieffect. The first draws the filament using an aspirator slot (slotdraw), which may run the width of the spinneret or the width of themachine. The second method draws the filaments through a nozzle oraspirator gun. Filaments formed in this manner may be collected on ascreen (“wire”) or porous forming belt to form the web. The web can thenbe passed through compression rolls and then between heated calendarrolls where the raised lands on one roll bond the web at pointscovering, for example, 10% to 40% of its area to form a non-wovenfabric. In another embodiment, welding of the fibers can also beeffected using convection or radiative heat. In yet another embodiment,fiber welding can be effected through friction by using hydro entanglingor needle punch methods.

Annealing may be done after the formation of fiber in continuousfilament or fabrication of a non-woven material from the fibers.Annealing may partially relieve the internal stress in the stretchedfiber and restore the elastic recovery properties of the blend in thefiber. Annealing has been shown to lead to significant changes in theinternal organization of the crystalline structure and the relativeordering of the amorphous and semicrystalline phases. This may lead torecovery of the elastic properties. For example, annealing the fiber ata temperature of at least 40° C., above room temperature (but slightlybelow the crystalline melting point of the blend), may be adequate forthe restoration of the elastic properties in the fiber.

Thermal annealing of the fibers can be conducted by maintaining thefibers (or fabrics made from the fibers) at temperatures, for example,between room temperature up to 160° C., or alternatively to a maximum of130° C. for a period between a few seconds to less than 1 hour. Atypical annealing period is 1 to 5 minutes at 100° C. The annealing timeand temperature can be adjusted based upon the composition employed. Inother embodiments, the annealing temperature ranges from 60° C. to 130°C. In another embodiment, the temperature is about 100° C.

In certain embodiments, for example, conventional continuous fiberspinning, annealing can be done by passing the fiber through a heatedroll (godet), without the application of conventional annealingtechniques. Annealing may desirably be accomplished under very low fibertension to allow shrinking of the fiber in order to impart elasticity tothe fiber. In non-woven processes, the web usually passes through acalender to point bond (consolidate) the web. The passage of theunconsolidated non-woven web through a heated calender at relativelyhigh temperature may be sufficient to anneal the fiber and increase theelasticity of the non-woven web. Similar to fiber annealing, thenon-woven web may desirably be accomplished under low tension to allowfor shrinkage of the web in both machine direction (MD) and crossdirection (CD) to enhance the elasticity of the non-woven web. In otherembodiments, the bonding calender roll temperature ranges from 100° C.to 130° C. In another embodiment, the temperature is about 100° C. Theannealing temperature can be adjusted for any particular blend.

The fibers and non-woven fabrics of the present invention can beemployed in several applications. In one or more embodiments, they maybe advantageously employed in diapers and/or similar personal hygienearticles such as adult incontinence apparel. In particular, they can beemployed as the dynamic or stretchable components of these articles suchas, but not limited to, the elastic fastening bands. In otherembodiments, the fibers and non-woven fabrics may be fabricated intoother protective garments or covers such as medical gowns or aprons,bedding, or similar disposable garments and covers.

In other embodiments, the fibers and fabrics of the present of thepresent invention can be employed in the manufacture of filter media.For example, particular applications include use in functionalizedresins where the non-woven fabric can be electrostatically charged toform an electret.

Specific Embodiments

Paragraph A: A method for forming a polymer blend, the methodcomprising: (i) charging to a reactive extruder a first polymer and asecond polymer to form an initial blend, where the first polymer is apropylene-based elastomer including up to 35% by weight ethylene-derivedunits and a heat of fusion, as determined according to DSC proceduresaccording to ASTM E-793, of less than 80 J/g and a melt temperature ofless than 110° C., where the second polymer is a propylene-based polymerhaving a melt temperature in excess of 110° C. and a heat of fusion inexcess of 80 J/g; (ii) after said step of charging, charging a peroxideto the initial blend to thereby form a reactive blend; (iii) conductingthe reactive blend at a flow rate through a series of barrels within theextruder; (iv) subjecting the reactive blend, in one or more barrels, tohigh shear mixing; (v) maintaining the temperature of the reactive blendat a temperature sufficient to decompose at least 50% of the peroxideand thereby form a reacted blend; (vi) restricting flow rate of thereacted blend through one or more barrels to increase the time that thereactive blend is subjected to the high shear mixing; (vii) removingcompounds from the reacted blend or the reactive blend; (viii)introducing an antioxidant to the reacted blend; (ix) increasing flowrate of the reacted blend through one or more barrels; (x) after saidstep of increasing the flow rate, passing the reacted blend through oneor more screens to thereby remove unwanted contaminates; and (xi)pelletizing the reacted blend.

Paragraph B: The process of paragraph A, where said step (v) includesmaintaining the temperature of the reactive blend at a temperaturesufficient to decompose at least 70% of the peroxide.

Paragraph C: The process of paragraphs A-B, where said step (v) includesmaintaining the temperature of the reactive blend at a temperaturesufficient to decompose at least 90% of the peroxide.

Paragraph D: The process of paragraphs A-C, where said step (v) includesmaintaining the temperature of the reactive blend to at least 165° C.

Paragraph E: The process of paragraphs A-D, where said step (v) includesmaintaining the temperature of the reactive blend to at least 185° C.

Paragraph F: The process of paragraphs A-E, where said step (iii)includes is charging at least 1,000 ppm peroxide based upon the weightof the propylene-based elastomer and the propylene-based thermoplasticresin combined.

Paragraph G: The process of paragraphs A-F, where said step (iii)includes charging at least 3,000 ppm peroxide based upon the weight ofthe propylene-based elastomer and the propylene-based thermoplasticresin combined.

Paragraph H: A method for forming a polymer blend, the methodcomprising: (i) charging to a reactive extruder a first polymer and asecond polymer to form a blend, where the first polymer is apropylene-based elastomer including up to 35% by weight ethylene-derivedunits and a heat of fusion, as determined according to DSC proceduresaccording to ASTM E-793, of less than 80 J/g and a melt temperature ofless than 110° C., where the second polymer is a propylene-based polymerhaving a melt temperature in excess of 110° C. and a heat of fusion inexcess of 80 J/g; (ii) after said step of charging, charging a peroxideto the blend to thereby form a reactive blend; (iii) conducting thereactive blend at a flow rate through a series of barrels within theextruder; (iv) subjecting the reactive blend, in one or more barrels, tohigh shear mixing; (v) maintaining the temperature of the reactive blendat a temperature of at least 165° C. for at least 5 seconds and therebyform a reacted blend; (vi) restricting flow rate of the reacted blendthrough one or more barrels to increase the time that the reactive blendis subjected to the high shear mixing; (vii) removing compounds from thereacted blend or the reactive blend; (viii) introducing an antioxidantto the reacted blend; (ix) increasing flow rate of the reacted blendthrough one or more barrels; (x) after said step of increasing the flowrate, passing the reacted blend through one or more screens to therebyremove unwanted contaminates; and (xi) pelletizing the reacted blend.

Paragraph I: The process of paragraph H, where said step (v) includesmaintaining the temperature of the reactive blend at a temperature of atleast 185° C. for at least 15 seconds.

Paragraph J: The process of paragraphs H-I, where said step (v) includesmaintaining the temperature of the reactive blend at a temperature of atleast 185° C. for at least 20 seconds.

Paragraph K: The process of paragraphs H-J, where said step (v) includesmaintaining the temperature of the reactive blend at a temperature of atleast 185° C. for at least 30 seconds.

Paragraph L: The process of paragraphs H-K, where said step (iii)includes charging at least 1,000 ppm peroxide based upon the weight ofthe propylene-based elastomer and the propylene-based thermoplasticresin combined.

Paragraph M: The process of paragraphs H-L, where said step (iii)includes charging at least 3,000 ppm peroxide based upon the weight ofthe propylene-based elastomer and the propylene-based thermoplasticresin combined.

Paragraph N: A composition prepared by the process of any of thepreceding paragraphs A-M.

Paragraph O: The composition of paragraph N comprising at least oneblock segment of the first polymer and at least one block segment of thesecond polymer.

Paragraph P: A method for forming one or more fibers, the methodcomprising: (i) charging to a reactive extruder a first polymer and asecond polymer to form an initial blend, where the first polymer is apropylene-based elastomer including up to 35% by weight ethylene-derivedunits and a heat of fusion, as determined according to DSC proceduresaccording to ASTM E-793, of less than 80 J/g and a melt temperature ofless than 110° C., where the second polymer is a propylene-based polymerhaving a melt temperature in excess of 110° C. and a heat of fusion inexcess of 80 J/g; (ii) after said step of charging, charging a peroxideto the initial blend to thereby form a reactive blend; (iii) conductingthe reactive blend at a flow rate through a series of barrels within theextruder; (iv) subjecting the reactive blend, in one or more barrels, tohigh shear mixing; (v) maintaining the temperature of the reactive blendat a temperature sufficient to decompose at least 50% of the peroxideand thereby form a reacted blend; (vi) restricting flow rate of thereacted blend through one or more barrels to increase the time that thereactive blend is subjected to the high shear mixing; (vii) increasingflow rate of the reacted blend through one or more barrels; (viii) aftersaid step of increasing the flow rate, passing the reacted blend throughone or more screens to thereby remove unwanted contaminates; (ix)extruding the reacted blend through a plurality of die capillaries toform one or more molten threads or filaments; and (x) attenuating themolten threads or filaments in a gas stream to form one or moremeltblown fibers.

Paragraph Q: The process of Paragraph P, where the reacted blend isextruded through the plurality of die capillaries at a rate greater thanor equal to 0.3 grams per hole per minute.

Paragraph R: The process of Paragraph P or Q, wherein the processfurther comprises depositing the meltblown fibers on a collectingsurface to form a web or fabric.

Paragraph S: A method for forming one or more fibers, the methodcomprising: (i) charging to a reactive extruder a first polymer and asecond polymer to form an initial blend, where the first polymer is apropylene-based elastomer including up to 35% by weight ethylene-derivedunits and a heat of fusion, as determined according to DSC proceduresaccording to ASTM E-793, of less than 80 J/g and a melt temperature ofless than 110° C., where the second polymer is a propylene-based polymerhaving a melt temperature in excess of 110° C. and a heat of fusion inexcess of 80 J/g; (ii) after said step of charging, charging a peroxideto the initial blend to thereby form a reactive blend; (iii) conductingthe reactive blend at a flow rate through a series of barrels within theextruder; (iv) subjecting the reactive blend, in one or more barrels, tohigh shear mixing; (v) maintaining the temperature of the reactive blendat a temperature sufficient to decompose at least 50% of the peroxideand thereby form a reacted blend; (vi) restricting flow rate of thereacted blend through one or more barrels to increase the time that thereactive blend is subjected to the high shear mixing; (vii) increasingflow rate of the reacted blend through one or more barrels; (viii) aftersaid step of increasing the flow rate, passing the reacted blend throughone or more screens to thereby remove unwanted contaminates; (xi)introducing the reacted blend to a spinneret to form one or morefilaments; and (x) quenching the filaments with air to form one or morefibers.

Paragraph T: The process of Paragraph S, wherein the process furthercomprises depositing the fibers on a collecting surface to form a web orfabric.

Paragraph U: The process of any one of Paragraphs P-T, where said step(v) includes maintaining the temperature of the reactive blend at atemperature sufficient to decompose at least 70% of the peroxide.

Paragraph V: The process of any one of Paragraphs P-U, where said step(v) includes maintaining the temperature of the reactive blend at atemperature sufficient to decompose at least 90% of the peroxide.

Paragraph W: The process of any one of Paragraphs P-V, where said step(v) includes maintaining the temperature of the reactive blend to atleast 165° C.

Paragraph X: The process of any one of Paragraphs P-W, where said step(v) includes maintaining the temperature of the reactive blend to atleast 185° C.

Paragraph Y: The process of any one of Paragraphs P-X, where said step(iii) includes charging at least 1,000 ppm peroxide based upon theweight of the propylene-based elastomer and the propylene-basedthermoplastic resin combined.

Paragraph Z: The process of any one of Paragraphs P-Y, where said step(iii) includes charging at least 3,000 ppm peroxide based upon theweight of the propylene-based elastomer and the propylene-basedthermoplastic resin combined.

Paragraph AA: The process of any one of Paragraphs P-Z, wherein theprocess further comprises introducing an antioxidant to the reactedblend.

Paragraph BB: A method for forming one or more fibers, the methodcomprising: (i) charging to a reactive extruder a first polymer and asecond polymer to form an initial blend, where the first polymer is apropylene-based elastomer including up to 35% by weight ethylene-derivedunits and a heat of fusion, as determined according to DSC proceduresaccording to ASTM E-793, of less than 80 J/g and a melt temperature ofless than 110° C., where the second polymer is a propylene-based polymerhaving a melt temperature in excess of 110° C. and a heat of fusion inexcess of 80 J/g; (ii) after said step of charging, charging a peroxideto the initial blend to thereby form a reactive blend; (iii) conductingthe reactive blend at a flow rate through a series of barrels within theextruder; (iv) subjecting the reactive blend, in one or more barrels, tohigh shear mixing; (v) maintaining the temperature of the reactive blendat a temperature of at least 165° C. for at least 5 seconds and therebyform a reacted blend; (vi) restricting flow rate of the reacted blendthrough one or more barrels to increase the time that the reactive blendis subjected to the high shear mixing; (vii) increasing flow rate of thereacted blend through one or more barrels; (viii) after said step ofincreasing the flow rate, passing the reacted blend through one or morescreens to thereby remove unwanted contaminates; (ix) extruding thereacted blend through a plurality of die capillaries to form moltenthreads or filaments; and (x) attenuating the molten threads orfilaments in a gas stream to form meltblown fibers.

Paragraph CC: The process of Paragraph BB, where the reacted blend isextruded through the plurality of die capillaries at a rate greater thanor equal to 0.3 grams per hole per minute.

Paragraph DD: The process of Paragraph BB or CC, wherein the processfurther comprises depositing the meltblown fibers on a collectingsurface to form a web or fabric.

Paragraph EE: A method for forming a fiber, the method comprising: (i)charging to a reactive extruder a first polymer and a second polymer toform a blend, where the first polymer is a propylene-based elastomerincluding up to 35% by weight ethylene-derived units and a heat offusion, as determined according to DSC procedures according to ASTME-793, of less than 80 J/g and a melt temperature of less than 110° C.,where the second polymer is a propylene-based polymer having a melttemperature in excess of 110° C. and a heat of fusion in excess of 80J/g; (ii) after said step of charging, charging a peroxide to the blendto thereby form a reactive blend; (iii) conducting the reactive blend ata flow rate through a series of barrels within the extruder; (iv)subjecting the reactive blend, in one or more barrels, to high shearmixing; (v) maintaining the temperature of the reactive blend at atemperature of at least 165° C. for at least 5 seconds and thereby forma reacted blend; (vi) restricting flow rate of the reacted blend throughone or more barrels to increase the time that the reactive blend issubjected to the high shear mixing; (vi) increasing flow rate of thereacted blend through one or more barrels; (viii) after said step ofincreasing the flow rate, passing the reacted blend through one or morescreens to thereby remove unwanted contaminates; (ix) introducing thereacted blend to a spinneret to form one or more filaments; and (x)quenching the filaments with air to form one or more fibers.

Paragraph FF: The process of Paragraph EE, wherein the process furthercomprises depositing the fibers on a collecting surface to form a web orfabric.

Paragraph GG: The process of any one of Paragraphs BB to FF, where saidstep (v) includes maintaining the temperature of the reactive blend at atemperature of at least 185° C. for at least 15 seconds.

Paragraph HH: The process of any one of Paragraphs BB to GG, where saidstep (v) includes maintaining the temperature of the reactive blend at atemperature of at least 185° C. for at least 20 seconds.

Paragraph II: The process of any one of Paragraphs BB to HH, where saidstep (iii) includes charging at least 1,000 ppm peroxide based upon theweight of the propylene-based elastomer and the propylene-basedthermoplastic resin combined.

Paragraph JJ: The process of any one of Paragraphs BB to II, where saidstep (iii) includes charging at least 3,000 ppm peroxide based upon theweight of the propylene-based elastomer and the propylene-basedthermoplastic resin combined.

Paragraph KK: The process of any one of Paragraphs BB to JJ, wherein theprocess further comprises introducing an antioxidant to the reactedblend.

Paragraph LL: A fiber prepared by the process of any one of ParagraphsP-KK.

Paragraph MM: A nonwoven composition formed by the fibers of ParagraphLL.

In order to demonstrate the practice of the present invention, thefollowing examples have been prepared and tested. The examples shouldnot, however, be viewed as limiting the scope of the invention. Theclaims will serve to define the invention.

EXAMPLES Example 1

A process in accordance with the present invention was demonstratedusing a BERSTORFF ZE-90A (Berstorff) co-rotating, intermeshing,twin-screw extruder. The is copolymer of propylene and ethylene,containing about 15 wt % of ethylene was metered into the feed throat ofthe extruder using a loss-in-weight screw feeder. A predominantlyisotactic homopolymer polypropylene was fed into the same feed throatusing another loss-in-weight screw feeder. The blend was treated byvis-breaking in the presence of a peroxide obtained under the tradenameLUPEROX 101 (Arkema). The barrel sections were assembled as described inTable I.

TABLE I Barrel Length Cumulative Cumulative Number Type mm mm L/D 1 FeedBarrel 450 450 5 2 Top Liquid Injector 450 900 10 3 Top Liquid Injector450 1350 15 4 Closed 450 1800 20 4.5 Transition 90 1890 21 5 Top Vent450 2340 26 6 Side Feed 450 2790 31 7 Closed 450 3240 36 8 Top Vent 4503690 41 9 Side Feed 450 4140 46 10 Closed 450 4590 51 10.5 Transition205 4795 Screen Pack 305 5100 Transition 150 5250 Die Plate 60 5310Pelletizer

The screw segments were assembled as shown in Table II.

TABLE II Extruder Berstorff Size 90A Ratio Length/Pitch Nr. of PieceCumulative or Starts Length Length, Type Pitch Lobes Or Angle Handing mmmm Barrel EA 75 1 2 75 75 1 A 125 1 2 125 200 1 A 125 1 2 125 325 1 A125 1 2 125 450 1 EA 125 1 2 125 575 2 KB 75 5 45 LI 75 650 2 EA 100 1 2100 750 2 EA 75 1 2 75 825 2 EA 75 1 2 75 900 2 KB 75 5 45 LI 75 975 3KB 75 5 45 LI 75 1050 3 KB 75 5 45 LI 75 1125 3 KB 75 5 45 RE 75 1200 3EA 75 1 2 75 1275 3 EA 75 1 2 75 1350 3 KB 125 5 45 LI 125 1475 4 KB 1255 90 LI 125 1600 4 EA 100 0.5 2 RE 50 1650 4 EA 100 1 2 100 1750 4 KB125 5 45 LI 125 1875 5 KB 125 5 90 LI 125 2000 5 EA 100 1 2 100 2100 5ZB 75 3 12 RE-LI 75 2175 5 ZB 75 3 12 RE-LI 75 2250 5 KB 125 5 90 1252375 6 EA 100 1 2 100 2475 6 ZB 75 3 12 RE-LI 75 2550 6 ZB 75 3 12 RE-LI75 2625 6 KB 75 5 90 75 2700 6 100 1 2 100 2800 7 ZB 75 3 12 RE-LI 752875 7 ZB 75 3 12 RE-LI 75 2950 7 EA 100 1 2 100 3050 7 EA 100 1 2 1003150 7 EA 100 1 2 100 3250 8 A 125 1 2 125 3375 8 A 125 1 2 125 3500 8 A125 1 2 125 3625 8 A 125 1 2 125 3750 9 EA 100 1 2 100 3850 9 EA 100 1 2100 3950 9 EA 75 1 2 75 4025 9 EA 75 1 2 75 4100 9 EA 75 1 2 75 4175 10EA 75 1 2 75 4250 10 EA 75 1 2 75 4325 10 EA 75 1 2 75 4400 10 EA 75 1 275 4475 10 EA 75 1 2 75 4550 10 ZE90A-120 0 GRD 0 4550 10

Table III provides the characteristics of the vis-breaking process.

TABLE III Production Rate lb/h 2000 Ethylene-Propylene Copolymer FeedRate lb/h 1700 Polypropylene feed rate lb/h 300 Luperox101 feed ratelb/h 6.5 Vent Zone Zone 8 Die Hole Dia inch 0.125 No. of Holes Open Nr.80 Pelletizer Hubs Spokes Nr. 2 Pelletizer Hub Blades Nr. 2 PelletizerSpring Color Red Screen OD inch 5.75 Screen Pack-Screen 1 Mesh 40 ScreenPack-Screen 2 Mesh 325 Screen Pack-Screen 3 Mesh 200 Screen Pack-Screen4 Mesh 80 Screen Pack-Screen 5 Mesh 40 Vent Zone Vacuum in Hg 27 ScrewSpeed rpm 250 Feed Zone Temp. F. cooled Extruder Zone 2 F. 298 ExtruderZone 3 F. 420 Extruder Zone 4 F. 461 Extruder Zone 4.5 F. 370 ExtruderZone 5 F. 458 Extruder Zone 6 F. 440 Extruder Zone 7 F. 403 ExtruderZone 8 F. 393 Extruder Zone 9 F. 304 Extruder Zone 10 F. 369 UpstreamMelt Psig Psig 315 Upstream Melt Temp. F. 419 Downstream Melt Psig Psig193 Downstream Melt Temp. F. 330 Die Plate F. 340 Pelletizer Speed rpm1750 Pelletizer amps amps 23 Product MFR 230

Example 2

A process according to the present invention was demonstrated using aWERNER-PFLEIDERER ZSK-90 (Werner-Pfleiderer, nka, Coperion) co-rotating,intermeshing, twin-screw extruder.

A gear pump was installed at the exit of the extruder, followed by ascreen changer, the die plate, and a pelletizer. A vacuum pump wasconnected to the vent port from Barrel 8. The polypropylene and theethylene-propylene copolymer were fed using independent loss-in-weightfeeders. The peroxide was injected in Barrel 2 using an injectionnozzle. The antioxidant, IRGAPHOS 168 (Ciba Specialties), was injectedas a slurry into the 6^(th) barrel of the extruder. A polyalphaolefin,SPECTRASYN 100 (ExxonMobil Chemical Co.), was used as the slurry medium.The process conditions are given below in Table IV. A product with amelt flow rate of 118 was obtained.

TABLE IV VM6200 Feed rate kg/h 297.5 PP3155 Feed rate kg/h 52.5Luperox101 feed rate kg/h 0.48 Antioxidant Slurry Feed Rate kg/h 1.4Irgaphos 168 Content wt % 25 SpectraSyn 100 Content wt % 75 PeroxidePort Location 2 UP/Under Antioxidant Port Location 6 Downstream VentZone Zone 8 Die Hole Dia inch 0.125 No. of Holes Open Nr. 25 PelletizerHubs Spokes Nr. 8 Pelletizer Hub Type Wobble Pelletizer Hub Blades Nr. 8Pelletizer Spring Color Red Screw Speed rpm 200 Extruder Power Used KW63 Screw Torque % 67 Feed Zone Temp. C. Cooled Extruder Zone 2 C. 115Extruder Zone 3 C. 203 Extruder Zone 4 C. 220 Extruder Zone 5 C. 222Extruder Zone 6 C. 222 Extruder Zone 7 C. 222 Extruder Zone 8 C. 168Extruder Zone 9 C. 140 Extruder Zone 10 C. 104 MFP Suction Pressure Psig122 Melt Gear Pump Temp. C. 194 MGP Discharge Pressure Psig 655 ScreenC. 150 Die Pressure Psig 525 Die Plate C. 131 Pelletizer Speed rpm 1491Pelletizer water Temp C. 26.8 Vac Pump Pressure in Hg 23.8

While the present invention has been described and illustrated byreference to particular embodiments, those of ordinary skill in the artwill appreciate that the invention lends itself to variations notnecessarily illustrated herein. For this reason, then, reference shouldbe made solely to the appended claims for purposes of determining thetrue scope of the present invention.

1. A method for forming one or more fibers, the method comprising: (i)charging to a reactive extruder a first polymer and a second polymer toform an initial blend, where the first polymer is a propylene-basedelastomer including up to 35% by weight ethylene-derived units and aheat of fusion, as determined according to DSC procedures according toASTM E-793, of less than 80 J/g and a melt temperature of less than 110°C., where the second polymer is a propylene-based polymer having a melttemperature in excess of 110° C. and a heat of fusion in excess of 80J/g; (ii) after said step of charging, charging a peroxide to theinitial blend to thereby form a reactive blend; (iii) conducting thereactive blend at a flow rate through a series of barrels within theextruder; (iv) subjecting the reactive blend, in one or more barrels, tohigh shear mixing; (v) maintaining the temperature of the reactive blendat a temperature sufficient to decompose at least 50% of the peroxideand thereby form a reacted blend; (vi) restricting flow rate of thereacted blend through one or more barrels to increase the time that thereactive blend is subjected to the high shear mixing; (vii) increasingflow rate of the reacted blend through one or more barrels; (viii) aftersaid step of increasing the flow rate, passing the reacted blend throughone or more screens to thereby remove unwanted contaminates; (ix)extruding the reacted blend through a plurality of die capillaries toform one or more molten threads or filaments; and (x) attenuating themolten threads or filaments in a gas stream to form one or moremeltblown fibers.
 2. The process of claim 1, where said step (v)includes maintaining the temperature of the reactive blend at atemperature sufficient to decompose at least 70% of the peroxide.
 3. Theprocess of claim 1, where said step (v) includes maintaining thetemperature of the reactive blend at a temperature sufficient todecompose at least 90% of the peroxide.
 4. The process of claim 1, wheresaid step (v) includes maintaining the temperature of the reactive blendto at least 165° C.
 5. The process of claim 1, where said step (v)includes maintaining the temperature of the reactive blend to at least185° C.
 6. The process of claim 1, where said step (iii) includescharging at least 1,000 ppm peroxide based upon the weight of thepropylene-based elastomer and the propylene-based thermoplastic resincombined.
 7. The process of claim 1, where said step (iii) includescharging at least 3,000 ppm peroxide based upon the weight of thepropylene-based elastomer and the propylene-based thermoplastic resincombined.
 8. The process of claim 1, where the reacted blend is extrudedthrough the plurality of die capillaries at a rate greater than or equalto 0.3 grams per hole per minute.
 9. The process of claim 1, wherein theprocess further comprises introducing an antioxidant to the reactedblend.
 10. The process of claim 1, wherein the process further comprisesdepositing the meltblown fibers on a collecting surface to form a web orfabric.
 11. A method for forming fibers, the method comprising: (i)charging to a reactive extruder a first polymer and a second polymer toform an initial blend, where the first polymer is a propylene-basedelastomer including up to 35% by weight ethylene-derived units and aheat of fusion, as determined according to DSC procedures according toASTM E-793, of less than 80 J/g and a melt temperature of less than 110°C., where the second polymer is a propylene-based polymer having a melttemperature in excess of 110° C. and a heat of fusion in excess of 80J/g; (ii) after said step of charging, charging a peroxide to theinitial blend to thereby form a reactive blend; (iii) conducting thereactive blend at a flow rate through a series of barrels within theextruder; (iv) subjecting the reactive blend, in one or more barrels, tohigh shear mixing; (v) maintaining the temperature of the reactive blendat a temperature of at least 165° C. for at least 5 seconds and therebyform a reacted blend; (vi) restricting flow rate of the reacted blendthrough one or more barrels to increase the time that the reactive blendis subjected to the high shear mixing; (vii) increasing flow rate of thereacted blend through one or more barrels; (viii) after said step ofincreasing the flow rate, passing the reacted blend through one or morescreens to thereby remove unwanted contaminates; (ix) extruding thereacted blend through a plurality of die capillaries to form moltenthreads or filaments; and (x) attenuating the molten threads orfilaments in a gas stream to form meltblown fibers.
 12. The process ofclaim 11, where said step (v) includes maintaining the temperature ofthe reactive blend at a temperature of at least 185° C. for at least 15seconds.
 13. A method for forming a fiber, the method comprising: (i)charging to a reactive extruder a first polymer and a second polymer toform a blend, where the first polymer is a propylene-based elastomerincluding up to 35% by weight ethylene-derived units and a heat offusion, as determined according to DSC procedures according to ASTME-793, of less than 80 J/g and a melt temperature of less than 110° C.,where the second polymer is a propylene-based polymer having a melttemperature in excess of 110° C. and a heat of fusion in excess of 80J/g; (ii) after said step of charging, charging a peroxide to the blendto thereby form a reactive blend; (iii) conducting the reactive blend ata flow rate through a series of barrels within the extruder; (iv)subjecting the reactive blend, in one or more barrels, to high shearmixing; (v) maintaining the temperature of the reactive blend at atemperature of at least 165° C. for at least 5 seconds and thereby forma reacted blend; (vi) restricting flow rate of the reacted blend throughone or more barrels to increase the time that the reactive blend issubjected to the high shear mixing; (vii) increasing flow rate of thereacted blend through one or more barrels; (viii) after said step ofincreasing the flow rate, passing the reacted blend through one or morescreens to thereby remove unwanted contaminates; (ix) introducing thereacted blend to a spinneret to form one or more filaments; and (x)quenching the filaments with air to form one or more fibers.
 14. Theprocess of claim 13, where said step (v) includes maintaining thetemperature of the reactive blend at a temperature of at least 185° C.for at least 15 seconds.
 15. The process of claim 13, where said step(v) includes maintaining the temperature of the reactive blend at atemperature of at least 185° C. for at least 20 seconds.
 16. The processof claim 13, where said step (iii) includes charging at least 1,000 ppmperoxide based upon the weight of the propylene-based elastomer and thepropylene-based thermoplastic resin combined.
 17. The process of claims13, where said step (iii) includes charging at least 3,000 ppm peroxidebased upon the weight of the propylene-based elastomer and thepropylene-based thermoplastic resin combined.
 18. The process of claim13, wherein the process further comprises introducing an antioxidant tothe reacted blend.
 19. The process of claim 20, wherein the processfurther comprises depositing the fibers on a collecting surface to forma web or fabric.
 20. A fiber prepared by the process of claim 1.